Bone Loss Stable on Restricted Calorie Diet

TUESDAY, Sept. 23 -- Overweight adults who eat a low-calorie diet that includes proper nutrition can lose weight and fat without experiencing significant bone loss, a new study says.

The study, by the team at Pennington Biomedical Research Center in Baton Rouge, La., included 46 healthy, overweight men and women (average age 37) assigned to one of four groups: The 11 participants in the control group ate a healthy diet; 12 others consumed 25 percent fewer calories than they expended per day; 12 created a 25 percent energy deficit by eating fewer calories and exercising five days a week; and 11 people ate a low-calorie diet (890 calories) a day until they achieved a 15 percent weight loss, at which time they switched to a weight maintenance plan.

All the diets contained the recommended levels of vitamin and minerals, and contained 30 percent fat, 15 percent protein and 55 percent carbohydrates, based on American Heart Association guidelines.

After six months, people in the control group had an average body weight reduction of 1 percent, compared with 10.4 percent in the calorie restriction group, 10 percent in the calorie restriction plus exercise group, and 13.9 percent in the low-calorie diet group.

At the start and end of the study, the researchers measured the participants' bone mineral density and blood markers of bone resorption and formation -- processes by which bone is broken down and regenerated on a regular basis.

"Compared with the control group, none of the groups showed any change in bone mineral density for total body or hip," the study authors wrote.

After six months, markers of bone resorption were increased in all three intervention groups. Markers of bone formation were lower in the calorie restriction group but remained the same in the low-calorie diet or calorie restriction plus exercise group.

"Our data do not support the notion that extreme weight loss (more than 10 percent) over short periods (three months) has a worse prognosis on bone health than gradual weight loss achieved over six months by moderate calorie restriction with or without aerobic exercise," the researchers wrote. "We speculate that in young individuals undergoing calorie restriction, minor adjustments in bone occur as a normal physiological adaptation to the reduced body mass. Further studies of longer duration are warranted and should include an assessment of bone architecture to ensure that bone quality is preserved with weight loss."

The study was published in the Sept. 22 issue of the journal Archives of Internal Medicine.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about weight loss.